Sodium content targets for pre-packaged foods, China: a quantitative study and proposal

Abstract Objective To determine the contribution of pre-packaged foods to population sodium intake in China, and to propose sodium content targets for food subcategories used for the World Health Organization’s (WHO’s) global sodium benchmarks. Methods The impact of four different approaches to reducing the sodium content of pre-packaged foods on population sodium intake was estimated using data from national databases covering the nutrient content and ingredients of 51 803 food products and food consumption by 15 670 Chinese adults. We recategorized food products using a food categorization framework developed for WHO’s global sodium benchmarks and adapted for China-specific foods. Findings Pre-packaged foods, including condiments, contributed 1302.5 mg/day of sodium intake per adult in 2021, accounting for 30.1% of population sodium intake in China. Setting maximum sodium content levels using a 90th-percentile target would reduce sodium intake from pre-packaged foods by 96.2 mg/day, corresponding to a 1.9% reduction in population intake. Using the 75th-percentile, a fixed 20% reduction and WHO benchmark targets would further reduce intake by 262.0 mg/day (5.2% population intake), 302.8 mg/day (6.0% population intake) and 701.2 mg/day per person (13.9% population intake), respectively. Maximum sodium content levels based on revised 20% reduction targets were proposed because they should result in substantial and acceptable reductions in sodium content for most food subcategories: overall sodium intake would decline by 305.0 mg/day per person, and population intake by 6.1%. Conclusion This study provides the scientific rationale for government policy on setting targets for food sodium content in China. Simultaneous action on discretionary salt use should also be taken.


Introduction
Sodium is an essential nutrient for which humans have a physiological need of as little as 200 to 500 mg/day. 1,2 The primary dietary contributor is the salt (i.e. sodium chloride) added during cooking or at the table, and hidden in processed foods. One gram of sodium is equivalent to 2.5 g of salt. Other sodium compounds, such as sodium glutamate, and some other food additives may also contribute to sodium intake.
Excessive sodium intake is associated with an increase in blood pressure and the risk of cardiovascular diseases and other chronic conditions. [3][4][5][6] Global burden of disease studies showed that excessive sodium intake led to 1.7 million deaths in China and 3.2 million deaths globally in 2017. 7,8 The World Health Organization (WHO) strongly recommends a sodium intake for adults of less than 2 g/day (i.e. 5 g/day of salt). 9 However, the current global average salt intake is estimated to be 10.78 g/day per person, which is more than double WHO's recommendation and far exceeds physiological requirements. 10 In many developed countries, pre-packaged food accounts for more than three quarters of population sodium intake. 11 Consequently, one of the best strategies for reducing sodium intake has been to harness the food industry to reformulate products by gradually lowering targets for sodium content. 12 WHO reports that 65 countries around the world, mostly highor middle-income countries, have implemented this policy. 10 In 2021, WHO established global sodium benchmarks for 58 subcategories of food that were based on the lowest feasible maximum value for each subcategory, as defined in existing national or regional targets. 13 These benchmarks provide a clear reference point for countries wishing to set or develop maximum sodium levels for foods. However, strategies for gradually reducing the sodium content of foods must avoid sharp reductions and the associated taste shock for consumers, especially in countries like China where dietary sodium primarily comes from cooking or table salt, and where consumers' taste preferences are largely influenced by foods prepared at home and in restaurants. 11,[14][15][16][17] Although the recommended sodium intake for individuals in China is the same as WHO's recommendation, the national goal set in 2016 was to reduce the population sodium intake by 20% by 2030, 18 which is more conservative than WHO's comparable global target of a 30% reduction by 2025. 13 As around 80% of sodium intake in China comes from salt and condiments added during cooking, 19,20 the government has been implementing several national salt reduction programmes since the 1990s that target catering and family cooks. 21 As a result, average household salt use decreased from 10.4 g/day per person Objective To determine the contribution of pre-packaged foods to population sodium intake in China, and to propose sodium content targets for food subcategories used for the World Health Organization's (WHO's) global sodium benchmarks. Methods The impact of four different approaches to reducing the sodium content of pre-packaged foods on population sodium intake was estimated using data from national databases covering the nutrient content and ingredients of 51 803 food products and food consumption by 15 670 Chinese adults. We recategorized food products using a food categorization framework developed for WHO's global sodium benchmarks and adapted for China-specific foods. Findings Pre-packaged foods, including condiments, contributed 1302.5 mg/day of sodium intake per adult in 2021, accounting for 30.1% of population sodium intake in China. Setting maximum sodium content levels using a 90th-percentile target would reduce sodium intake from pre-packaged foods by 96.2 mg/day, corresponding to a 1.9% reduction in population intake. Using the 75th-percentile, a fixed 20% reduction and WHO benchmark targets would further reduce intake by 262.0 mg/day (5.2% population intake), 302.8 mg/day (6.0% population intake) and 701.2 mg/day per person (13.9% population intake), respectively. Maximum sodium content levels based on revised 20% reduction targets were proposed because they should result in substantial and acceptable reductions in sodium content for most food subcategories: overall sodium intake would decline by 305.0 mg/day per person, and population intake by 6.1%. Conclusion This study provides the scientific rationale for government policy on setting targets for food sodium content in China. Simultaneous action on discretionary salt use should also be taken.
in 2010 to 2012 to 9.3 g/day per person in 2015, 22 still above recommended level.
Nevertheless, despite the continuing increase in the sale of pre-packaged food in China and the relatively high sodium content of pre-packaged food, [23][24][25][26][27] efforts to reduce sodium content by promoting food reformulation in the country have been very limited. Until now, except for policy on the mandatory labelling of the sodium content of pre-packaged foods, no official regulation has been issued to incentivize industry to reduce salt use. There exists only the set of voluntary sodium targets included in the Guideline for Salt Reduction for the Chinese Food Industry, which was issued in 2019. 28 The Guideline sets mean and maximum levels for the sodium content of individual food categories in China's unique food categorization framework, but sodium target levels were derived using data on only 9000 food products.
With the aim of accelerating the reduction in population sodium intake in China by reformulating pre-packaged foods, we explored the contribution of these foods to sodium intake, and assessed the potential impact of different approaches to reducing the sodium content of foods on population intake. In addition, we propose a set of maximum sodium target levels for different food subcategories to inform government policy on target setting.

Methods
The study involved data from two national databases covering the nutrient content and ingredients of pre-packaged foods and food consumption by Chinese adults, respectively. This study was approved by the Institutional Review Board of the National Institute for Nutrition and Health, Chinese Center for Disease Control and Prevention (no. 2018-005).
The Chinese pre-packaged food database contains information on the nutrient content and ingredients of prepackaged foods available for sale on the Chinese market. 29 Data collection started in March 2017 using Shixianzhi, a local FoodSwitch app (George Institute for Global Health, Newtown, Australia) for WeChat (Tencent Holdings Ltd, Shenzhen, China). 25,30 Between 2017 and 2018, data on 32 000 products were collected from the top 10 supermarkets in two provincial capitals in north and south China, respectively. Since January 2019, the food database has constantly been supplemented by consumers nation-wide using crowdsourcing. 29,31 During crowdsourcing, data were collected only on products that did not already exist in the Shixianzhi database to avoid duplication. For this study, we examined data on 76 354 products collected between March 2017 and February 2021. We excluded products that contained almost no sodium, pure sodium compounds, baby foods and products whose sodium content was unknown.
Food consumption data were obtained from the China Health and Nutrition Survey, 32 an ongoing longitudinal household-based survey initiated in 1989 and conducted every 2 to 4 years, that was established to study the effect of socioeconomic change on nutrition and health. Households across different geographical regions of China with varying levels of economic development were selected using a multistage, random-cluster, sampling strategy. 32 In each survey, trained interviewers interviewed all family members. Information on the consumption of individual foods was collected using three consecutive 24-hour dietary recalls on two weekdays and one weekend day, respectively. The name and amount of each food consumed, including pre-packaged foods, were recorded. 33 For our study, we used data on pre-packaged food consumption collected in 2018 from all 15 670 adult survey participants in 15 provinces.
Initially, food products were categorized using a hierarchical category tree developed by the Global Food Monitoring Group. 34 However, for our study, we recategorized all products in line with the food categorization framework used for WHO's global sodium benchmarks. 13 During this process, we excluded the existing category 5 (edible ices) because there was no product in this category on the Chinese market, and we added a new category 19 (egg and egg products) because there were hundreds of egg products with a relatively high sodium content in China. In addition, we added some new subcategories and redefined or expanded the descriptions of some subcategories to take into account China-specific food products. Details are available from the online repository. 35 The original WHO category and subcategory names were unchanged. Our analysis and results are based on this adapted categorization.

Statistical analysis
All sodium content values were converted into mg/100 g of food product.
For each product subcategory, sodium content is described using the mean, standard deviation (SD), standardized SD (i.e. the SD divided by the mean), minimum, maximum and the 25th, 50th (i.e. median), 75th and 90th percentiles.
The population sodium intake attributable to pre-packaged foods is the sum of the sodium intake of all individual food subcategories and is expressed in mg/day per person. Sodium intake from each subcategory was calculated as the median sodium content of foods in the subcategory (in mg/100 g) multiplied by their consumption (in g/day per person) and divided by 100, where consumption of food in a subcategory (in g/day per person) was the total amount of food in the subcategory consumed over three days by all survey participants (in g) divided by the total number of participants and divided by 3.
Following the approach used to establish WHO's sodium benchmarks, we decided to set individual maximum sodium target levels for each food subcategory. We considered three different types of targets in exploring suitable maximum sodium food content levels: (i) percentile targets; (ii) fixed percentage reduction targets; and (iii) WHO benchmarks. With the 75th percentile target, the 25% of food products in each subcategory that had a sodium content above the 75th percentile for that subcategory were reformulated to ensure their sodium content did not exceed the existing 75th percentile. With the 90th percentile target, an analogous 10% of food products in each subcategory were reformulated to ensure their sodium content did not exceed the 90th percentile. For a fixed percentage reduction target, the goal was to achieve a fixed percentage reduction in mean sodium content from baseline in each subcategory. With this approach, the projected maximum sodium content of individual food products in a subcategory was reduced reiteratively in steps of 1 mg/100 g until the desired percentage reduction in the mean sodium content of the whole subcategory was achieved. In each step, only products with a sodium content above the maximum for that step would have to be reformulated. In our study, we considered only a 20% reduction in sodium content, which reflects the national goal of a 20% reduction in sodium intake by 2030.
Several indicators were used to reflect the impact of different maximum sodium target levels on the number of foods to be Sodium content targets for food, China Puhong Zhang et al.
reformulated and on sodium intake, and to guide the selection of the most suitable targets. It was assumed that target levels had been achieved and that the sodium content of products would not change once these targets had been achieved. The indicators were: (i) the proportion of products in each food subcategory that would have to be reformulated (i.e. the proportion of products with a sodium content above the subcategory target); (ii) the resulting reduction in mean sodium content for each subcategory (i.e. the difference in the mean sodium content of foods in the subcategory, before and after reformulation, in mg/100 g); (iii) the resulting reduction in population sodium intake from a subcategory, in mg/day per person, calculated as the reduction in sodium content for the subcategory (in mg/100 g) multiplied by the amount consumed from the subcategory (in g/ day per person) and divided by 100; and (iv) the resulting reduction in sodium intake from all pre-packaged foods (i.e. the sum of the individual reductions across all subcategories).
The impact of different target levels could be seriously affected by the distribution of, or variation in, sodium content across foods in a subcategory. Consequently, to help identify the most suitable targets, we drew scatter plots to visualize the relationship between: (i) the reduction in mean sodium content achieved in a subcategory if targets were met, and the standardized SD in sodium content for that subcategory; and (ii) the proportion of products in a subcategory that would have to be reformulated if targets were met, and the standardized SD in sodium content for that subcategory.

Selection of maximum targets
Our recommended sodium target levels were based on two criteria. First, the targets should result in a relative reduction in sodium intake from all pre-packaged foods consistent with the national 20% reduction goal, while bearing in mind that discretionary salt use, which dominates consumption in China, must be similarly reduced in parallel. Second, the targets should result in a substantial and acceptable reduction in sodium content for each food subcategory, especially for the main sodium contributors, and consider: (i) the effect of the sodium content reduction on consumers' changing taste for salt; and (ii) the challenges posed to food producers by the number of foods that have to be reformulated.

Results
Of 76 354 pre-packaged food products in the Chinese database, 67 027 (87.8%) were recategorized into 62 subcategories of 18 main categories based on our adapted WHO categorization framework, and 51 803 (67.9%) in 55 subcategories of 15 main categories were eligible for inclusion in the analysis (Fig. 1). The 2018 China Health and Nutrition Survey reported on 3020 products in 51 subcategories consumed by 15 670 adults. Details of consumption for each food subcategory are available from the online repository. 35

Sodium content of foods
The sodium content of different Chinese food product subcategories is listed in Table 1 and is described in detail in the online repository. 35 Mean sodium content ranged from 93 mg/100 g to 7129 mg/100 g and the standardized SD ranged from 0.38 to 2.82. Sodium intake per adult from pre-packaged foods based on the median sodium content of individual subcategories was 1302.5 mg/day (i.e. 3.3 g of salt; Table 2); this accounted for 30.1% of population salt intake in China, which was 11 g/day per person in 2020. 36 The subcategory of soy sauce and fish sauce contributed most to sodium intake (median: 616.6 mg/day per person, which accounted for 47.3% of the 1302.5 mg/day from all pre-packaged foods), followed by the categories of ready-to-eat meals, and of salted butter, butter blends, margarine and oil-based spreads. The top six and top 12 subcategories accounted for 83.4% and 95.1% of sodium intake from all pre-packaged foods, respectively ( Table 2). • 7914 contained almost no sodium (i.e. candy, chocolate, sugar, edible oil and purified water); • 511 were pure sodium compound products (i.e. edible salt, baking soda, monosodium glutamate and chicken essence); and • 902 were baby food products 10 722 products excluded because they were in subcategories or main categories of products with no or little added salt:   Table 3 shows the maximum sodium content levels, the proportion of food products to be reformulated, and the estimated sodium content reduction in food subcategories when different types of maximum sodium content target were adopted. To achieve the 90th percentile, 75th percentile, 20% reduction and WHO benchmark targets, 10.0%, 25.0%, 25.0% and 46.9%, respectively, of all food products would have to be reformulated. As a result, sodium intake from prepackaged foods would fall from a baseline mean of 1514.0 mg/day per person by 96.2 mg/day per person (6.4%; 90th percentile target), 262.0 mg/day per person (17.3%; 75th percentile target), 302.8 mg/ day per person (20.0%; 20% reduction) and 701.2 mg/day per person (46.3%; WHO benchmark). The change in mean provides a good estimate of the effect of the targets, because reformulation impacts only products with a particularly high sodium content and, consequently, the median may be little changed. The corresponding reductions in mean population sodium intake with the four targets would be 1.9% (90th percentile), 5.2% (75th percentile), 6.0% (20% reduction) and 13.9% (WHO benchmark), given that 30.1% of population sodium intake comes from pre-packaged foods.

Different types of targets
In the analysis, we found that the reduction in mean sodium content with percentile targets varied greatly across subcategories and was positively corre-lated with the standardized SD for sodium content in the subcategories (Fig. 2). In addition, with the 20% reduction target, the proportion of food products that had to be reformulated in a subcategory correlated negatively with the standardized SD (Fig. 3). In contrast, with the WHO benchmarks, the proportion to be reformulated had no clear association with the standardized SD (Fig. 3). On examining the data in Table 1, Table 2, Table 3, Fig. 2 and Fig. 3 together, we found that several major sodium contributors, such as soy sauce and fish sauce (subcategory 18f) and wholemuscle meat products with non-heat preservation (subcategory 14f), had relatively high and stable sodium contents (i.e. a standardized SD less than 0.5). Although a greater number of products in these two subcategories should be reformulated, the 75th percentile target, for example, would lead to only a small reduction in sodium content (e.g. 6.9% for subcategory 18f and 5.6% for subcategory 14f; Table 3). In contrast, with the 20% reduction target, a fixed reduction in sodium content of 20% would be guaranteed for all subcategories; however, in subcategories with a large, standardized SD, too few products would have to be reformulated.

Sodium content targets
Among the different types of sodium content target we investigated, both the 75th percentile and the 20% reduction targets would reduce mean sodium intake from packaged foods by about 20%: the reductions would be 17.3% and 20%, respectively. After taking into account our criteria for selecting suitable targets and the results of our analysis, our initial proposal was that the 20% reduction target should be used for 47 food subcategories, and the 90th percentile target should be used for eight (Table 4). The 90th percentile target was used for the eight subcategories in which fewer than 10% of products would have had to be reformulated if the 20% reduction target were adopted. This proposal could lead to a reduction in sodium intake from pre-packaged foods of 305.0 mg/day per person, which represents a reduction of 20.1% from a baseline mean of 1514 mg/ day per person, and a 6.1% reduction in population sodium intake in China. (Table 4).

Discussion
Our study was triggered by the establishment of WHO's global sodium benchmarks for different food categories, and the approach employed in developing those benchmarks. We found that prepackaged foods accounted for a median sodium intake of 1302.5 mg/day per adult in China, which was 30.1% of population sodium intake. If all pre-packaged foods met WHO's global sodium benchmarks, sodium intake would be 701.2 mg/day per person (46.3%) lower, equivalent to a 13.9% reduction in mean population sodium intake. After considering different types of sodium content targets for use in China, we proposed a set of revised 20% Food product subcategory classification and description a,b (n = 55)

No. food products in subcategory
Sodium content of food products c (mg/ 100 g) d  1a. Granola and cereal-type bars   with some adaptation to take China-specific food products into account.

Mean (SD) Standardized
b With the 90th percentile target, 10% of products in each category had to be reformulated.
c With the 75th percentile target, 25% of products in each category had to be reformulated.  SD: standard deviation. Note: R 2 represents the proportion of the variance in the dependent variable (i.e. the reduction in mean sodium content of foods in the subcategory after the target has been achieved) that is explained by the independent variable (i.e. the standardized standard deviation of the sodium content of food products in the subcategory) in a linear regression model. Food subcategories were derived from the World Health Organization's food categorization framework, 13 with some adaptation to take China-specific food products into account. reduction targets because of their ability to induce a substantial and acceptable reduction in sodium content for most food subcategories.
In 2017, China's National Nutrition Plan prioritized improving nutrition laws, policies and standards. 37 As a key strategy for sodium intake reduction, setting sodium content targets for pre-packaged foods has been a hot topic, but has been held back largely by the lack of robust and reasonable sodium targets. Our proposal of revised 20% reduction targets could be a good starting point because these targets will: (i) encourage the reformulation of food products with a relatively high sodium content; (ii) guarantee a substantial reduction in sodium content (i.e. around 20% for each food subcategory), which may not be noticed by consumers and should be acceptable to most food companies; 38,39 and (iii) help achieve the national goal of a 20% reduction in population sodium intake by 2030. Recent modelling indicates that, should the proposed targets be met and maintained until 2030, around 6 million cardiovascular disease events could be prevented. 40 Moreover, if this approach proves successful, targets could be gradually lowered further towards WHO's benchmarks and food reformulation could play a leading role in reducing sodium intake nationally. However, even meeting WHO's benchmarks would reduce population sodium intake by only 13.9%. Consequently, authorities should simultaneously implement strategies targeting discretionary salt use during cooking and eating at home and in restaurants.
We found that a small number of food subcategories with a high sodium content or a large consumption, or both, accounted for almost 90% of sodium intake and could, if the targets were achieved, contribute almost 90% to the reduction in sodium intake from prepackaged foods. There is, then, an opportunity to start target setting, voluntarily or mandatorily, with these priority foods, thereby ensuring the initial organizational, supervisory and evaluation workload is low. Other countries have considerable experience in setting targets for priority foods, especially as a starting point. [41][42][43] Mandatory reformulation generally appears to achieve larger reductions in population-wide salt consumption than voluntary reformulation. 44  with some adaptation to take China-specific food products into account.
c Targets were based on the 20% reduction target, except where indicated by the superscript letter e. d For each subcategory, the reduction in population sodium intake was calculated as the reduction in mean sodium content (mg/100 g) multiplied by consumption (g/day per person; Table 2) and divided by100.
e The maximum sodium content target for this subcategory was based on the 90th-percentile target. f The overall proportion of products to be reformulated across all subcategories was the sum of the number of products to be reformulated in each subcategory divided by the total number of products.

Research
Sodium content targets for food, China Puhong Zhang et al.
is low, and robust monitoring with the publication of findings. 45 To make full use of WHO's food categorization framework and ensure comparability between countries, we tried to minimize changes to the framework. We noticed, however, that some subcategories (e.g. various processed meat and egg product subcategories) had very similar sodium concentrations. Further consolidation of these categories might simplify the implementation of food sodium content targets.
Initially, we considered only two strategies for setting maximum targets: (i) fixed percentile targets (e.g. 50th, 75th and 90th percentiles); and (ii) existing maximum targets, such as WHO's benchmarks. However, subsequent analysis showed that percentile targets had limitations: they resulted in only a very small reduction in the mean sodium content of food subcategories that had a small variation in sodium content between products, even though these products could have a very high sodium content and could be the main contributors to dietary sodium. For this reason, we proposed targets based on the 20% reduction strategy. We did not simulate the impact of targets included in the Guideline for Salt Reduction for the Chinese Food Industry because these targets were based on only around 9000 food products compared with our 51 803, and because they were derived by simply multiplying the highest sodium content in individual food categories by 90% or 80%. 28 Moreover, we wanted to build on WHO's sodium benchmarks, and the Guideline's food categorization framework is totally different from WHO's framework.
Our study had several limitations that could affect the extrapolation of our findings. First, we excluded some products that naturally contain sodium but no added salt, such as milk. Although this is reasonable when evaluating the effect of food reformulation on sodium intake, we may have slightly underestimated the overall contribution of pre-packaged foods to population sodium intake, and slightly overestimated the relative effect of sodium content reduction. Second, consumption-weighted sodium content reduction was based on the consumption of foods in a subcategory as a whole rather than on the consumption of individual foods. This approach may have influenced our calculations for subcategories in which the consumption of different products was uneven. Third, the consumption data set lacked participating families from west China, where the consumption of pre-packaged foods is likely to be lower than in central and east China. This exclusion may have led to the contribution of pre-packaged foods to sodium intake being overestimated. Fourth, we did not consider setting targets for priority food categories in the study, although our findings help make this possible.
In conclusion, pre-packaged food contributes to nearly one-third of population sodium intake in China and its market share is increasing. Reformulating foods is an important part of the solution. Although they will not bring sodium intake down to the level achievable with WHO's global sodium benchmarks, our revised 20% reduction targets provide a valuable starting point for government policy. We strongly recommend that action on dietary salt in China should involve comprehensive strategies that simultaneously target both sodium in pre-packaged food and discretionary salt use. 